Fan



d Patented Apr. 1.6,V 1946 James G. De Flon,

to The Fluor FAN 'Los Angeles. caux.. Corporation, Ltd., Los Calli'., a corporation of California' assisnor Angeles,

Application February 22', 1.943, Serial No. 476,738.

(Cl. 23d- 120)A li Claim.`

'This invention relates to improvements in fan assemblies, for example of the type used in mechanical draftcooling towers, and has for its` general object to obviatev certain conditions causing loss of eiiiciency and air moving capacity of such fans, to the end that the displacement and distribution of air by the same will be materially improved. To illustrate a practical though typical embodiment,\the invention will be described in a ian and ring assembly for mechanical draft cooling towers.

Cooling tower fanassemblies comprise a circular ring containing a centered fan operating in forced draft' towers to discharge air into the .flower portion of the water cooling chamber, and

in induced draft towers to draw the lair upwardly through the cooling chamber. Air displacement by theI fan occurs predominately in a swirling course owing in the direction of fan rotation and away from the fan. Investigationshave revealed that the usual fan and ring assembly operates at'less than its potential effective air moving capacity by reason of a condition of reverse air ilow existing beyond the the ,fan blades, or in the annular space between the fan ring and the path of the blade ends.

Rotation of the fan acts not only to displace the air in one direction through and beyond the body of the fan, but also to cause reverse flow of substantial amounts of air from the discharge side of the fan. through the aforementioned space 'by the inner portion of fan displaced air. In other words, the effective working length of the blades is increased. TheseI results are accomplished by the use of radially shortdeectorlvanes, simple and economical to install, which permitthe bulk of the air displaced the fan to assume its normal course 4of' ow. l

All the features of the invention,as well as the details of atypical embodiment thereof, will be understood from the following description of the accompanying drawing, in which;

Fig. 1 is a diagrammatic cross-sectional view illustrating the fan and ring assembly applied to a forced'draft tower;

Fig. 2 is a similarview illustrating an adaptation of the invention to-an ,induced draft tower;

Fig. 3 is an enlarged view of the fan and ring assembly; and

Fig. 4 is a 'fragmentary plan on line 4 4 of Fig.A 3."

Fig.1'shows a conventional forced draft water cooling ,tower comprising a vertically extending chamber lil enclosed by side Walls II and I2,

and into the upper interior of which water tol header I3 be cooled is sprayedI downwardly from over a suitable arrangement of decks or bailies I4, the cooled water finally being collected in ybasin I5. Air-is discharged byfthe fan'assembly adjacent the fan ring. The net result is a loss of the desired maximum quantity of air flow through the cooling chamber, and a reduction of air distribution therein that otherwise would occur if the air flow through the fan, ring were uni-directional to the full outer radial extent of its opening. i

This usual state of reverse air ilow within the f an ring is vovercome by the invention through the use of individual baiiles placed directly beyond the end portions of the blades at the discharge side of the fan, and serving to intercept and divert in the direction of the main airflow, the eddying streams tending to pass reversely beyond the blades. In its preferred form the baille assembly comprises a series of circularly spaced A of the bailies being to l ance of desired conditions I6 through the usual plenum lchamber Il into and upwardlythrough the cooling chamber I'Il in intimate contact with water being filmed over the' decks I 4. Mist eliminators I8 at the top of the chamber remove entraired water from the air leaving the chamber.

In the induced draft type of tower shown in Fig. 2, the fan and ring assembly mounted in the top wall 20 of the cooling chamber 2 I, draws air inwardly through inlets22 in the lower vchamber side walls 23, and` thence upwardly through the decks 24 inl counterrflow to water being sprayed from header 25. The particular form of induced draft tower shown has slatted baiiles 26 at the outside of the inlets 22 and spaced at 2l from the cooling chamber wall, the principal purposes cause the air to ilow downwardly and inwardly through the spaces 21 and baies into the cooling chamber, and to baille at mosphericA winds suiliciently to prevent disturb- 4 of air circulation Within the tower.

The features with which the invention is primarily concerned, are more particularly illustrated in Figs. 3 and 4 showing a fan and ring assembly adaptable, as will be understood, for use in either type of tower shown in Figs. 1 and Awhich preferably is shaped to have a, widely flaring mouth 3S giving the ring Venturi characteristics facilitating and streamlining the passage of air into and through the ring. The blade ends are spaced at 35 from the fan ring a distance subject to some variation in fan and ring assemblies of different sizes. In a typical instance the fan diameter may be 144 inches and the internal diameter of the ring about 146% inches.

The normal tendency of the fan is to discharge the air toward the right, as viewed in Fig. 3, in a swirling and advancing path of ow. Adjacent the surface of the fan ring, the air assumeslnot only a, circular and advancing swirl, but also a reverse direction of flow in eddying backward between the fan ring and the path of the blade ends. The result is a corresponding loss in the eilective air displacement and elciency of the fan, and a reduction of the air distribution at the discharge side of the fan. My primary object is to substantially eliminate such lay-passing of the air beyond the fan periphery, to increase both the quantity and spread of the air stream being moved by the fan.

This object is achieved by providing within the fan ring directly opposite the end portions of the blades 3l, a circular series of vanes 3l. The number of such vanes is variable, although as typical, Id may be usedvin a fan ring o- 1461/2 inches diameter. Referring to Fig. 4, the vanes preferably are arranged to extend angularly away from the plane of fan rotation in the direction that the fan rotates and in substantial corre spondence with the direction or course of air ow from the blades. Satisfactory results have been had with the gvanes 31 placed at an angle of about 30 with line 39 paralleling the plane of fan rotation. As further illustrative, the radial extent of the vanes toward the fan axis may be around 5 inches, with a space of about 1 inch left at dll between the inner ends of the vanes and the edges oi the fan blades.' It will be understood that the vanes may be positioned in any suitable manner. as by welding their inner edges to the ian ring.

The vanes 3i are placed sumciently close to the fan to intercept and divert that portion of the air at the blade terminals normallytending, as previously explained with reference to Fig. 5, to

vreverse its ow through space 35 toward the inlet side of the fan. To avoid undesirably abrupt diversion and deection of the air, the vanes are extended at an angle generally inthe direction of the swirling and advancing path taken by the air. By thus eliminating'the by passing of'air within the fan ring. more eiicient water cooling occurs within the tower chamber due both to the increased quantity of air circulation and the greater distribution resulting from the air ow within the fan ring being extended to its full area.

Increased eiciency also has resulted from the use of differential diameter hub plates on the fan 28. As shown in Fig. 3, the longitudinal axes of the blades 3l are offset from the axes of the arms 32. Accordingly, the vcorners 3|a ofthe blades lie on a. circle of smaller diameter than the further offset corners lblof the blades. The hub portion of the fan carries a pair of circular plates M and 42, the former having a smaller radius correspon'ding radial distance of the blade corners Sla from the `axis of shaft 30, while the larger radius of plate 42 corresponds substantially to, or is slightly greater than vthe radial distance of blade corner Sib from the projected axis of shaft all. Plates M and 42 prevent ow of air through the central portion of the fan at the inside of the blade ends, and thus avoid the loss of eiiiciency and air displacement that otherwise would result from the churning action of the blade arms` 32 on the air, and any reverse air iiow'at the center of the chamber. v

I claim:

In a stationary fan installation, the combination comprising a multiple blade fan, a ring surrounding and spaced from the ends of the ian blades, said ring having at the inlet 'side of the fan a widely ared mouth, circularly spaced vanes positioned entirely at the discharge side of the fan directly beyond the end portions of the blades and extending radially inward short distances from the ring so that th vanes are impinged only by the air displaced at the tip portions of the fan blades, said varies substantially preventing reverse flow ofv air under the iniluence of pressure differential between the inlet and outlet of the said ring.

JAMES G. DE FLON.

to, or being slightly greater than the 

